1. Field of the Invention
The present invention relates to inkjet inks, and, more particularly, to yellow inkjet inks having improved print quality with porous media.
2. Description of the Related Art
Thermal inkjet printing, to which this invention relates, is a commonly practiced form of printing. Thermal inkjet printing involves intense heating of an aqueous ink in a small amount in contact with a heating element so the ink is vaporized. The vaporized ink, including solids in the ink, is then expelled through a nozzle and subsequently jetted to an intended substrate, such as, for example, paper.
The composition of an inkjet ink is traditionally comprised of deionized water, a water-soluble organic solvent, and a colorant. The colorant may be a soluble dye or insoluble pigment. Traditionally, pigment based inks may have some disadvantages as compared to dye based inks as traditional pigment based inks tend to have slightly higher solids and viscosity which may pose to be more difficult for jetting through relatively smaller nozzle printhead designs. For example, due to the insolubility of pigments in water, polymeric dispersants and/or surfactants are typically added to improve the dispersibility of the pigment. The addition of a polymeric dispersant can increase the viscosity of an ink, and a viscous ink may be more difficult to jet in a printhead.
Inkjet printers may use dye-based color inks or pigment-based color inks. Dye-based color inks tend to be more saturated and more robust to inkjet pens. In contrast, pigment-based color inks tend to be more permanent and of the quality typically recognized with laser-like printers.
There is a very limited choice of pigments for use with pigment-based color inks, whereas the number of dyes to be used with dye-based color inks continuously grows.
A current challenge in the industry is to develop faster drying dye-based inks for use with porous photo media, rather than for use with traditional swellable polymer photo media. However, porous photo media are comprised of inorganic materials that, in conjunction with ozone gasses and light, interact with dyes such that the dyes fade and degrade.
What is needed in the art is a yellow dye-based inkjet ink that may be used with porous photo media with substantially minimal fading and degradation of the yellow dye.